1986 Dvorak established a CT Scan with rotational views which is supposed to measure the degree of rotation of the upper cervical spine that is mainly limited by the ligamentum alaria.
The patient is in a supine position.
First images in neutral position are taken.
Then the patient has to rotate the head to the right and to the left (90 degrees if possible).
The head is fixed to avoid any involuntarily movement.
Additional images in flexion can be taken.
It takes only a couple of minutes to perform each measurement which makes it bearable for the patient.
CT scans mostly allow the evaluation of bones. The rotational views are especially good to show cranio-cervical or alanto-axial instability (rotatory instability).
There is always a radiation exposure with CT scans and because of this fact it should only be done with a clear suspicion of a cervical spine pathology. Also it is very important that the radiologist knows exactly how to do this kind of imaging.
Publications about the establishment of the Dvorak CT:
Dvorak J, Penning L, Hayek J, Panjabi MM, Grob D, Zehnder R. Functional diagnostics of the cervical spine using computer tomography. Neuroradiology. 1988 Apr 1;30(2):132-7.
DVORAK J, PANJABI M, GERBER M, WICHMANN W. CT-Functional Diagnostics of the Rotatory Instability of Upper Cervical Spine: 1. An Experimental Study on Cadavers. Spine. 1987 Apr 1;12(3):197-205.
DVORAK J, HAYEK J, ZEHNDER R. CT-Functional Diagnostics of the Rotatory Instability of the Upper Cervical Spine: Part 2. An Evaluation on Healthy Adults and Patients with Suspected Instability. Spine. 1987 Oct 1;12(8):726-31.